The present invention relates to adhesion proteins and to methods of using them, e.g., to promote the adhesion of cells to a substrate, e.g., to human dermis. In particular, overlapping cDNA clones encoding the entire laminin B1k chain and recombinant proteins expressed therefrom are disclosed.
The structure of the prototype laminin, a glycoprotein component of most, if not all, basement membranes has been well described in a number of species. Its overall appearance, as visualized by rotary shawdowing, is cross-shaped with a single long arm arising from the coiled-coil interaction of three separate polypeptide chains and three short arms, each originating from the individual polypeptide chains. The three chains are: A, typified by the Ae chain of EHS laminin (400-kD); B1, typified by the B1e chain of EHS laminin (220-kD); and B2, typified by the B2e chain of EHS laminin (210-kD) chains. The primary structure for each of the three prototypic polypeptide chains in humans has been elucidated by overlapping cDNAs.
Additional polypeptides that are related to the laminin chains have been identified. A rat B1 chain homologue, s-laminin (B1s), has been identified. A human A chain homologue, merosin (Am), has been described and is the same as a homologue A chain found in mouse and bovine heart. Both chains can combine with the laminin A, B1 or B2 chains to form the variant trimeric proteins [Ae, B1s, B2e], [Am, B1e, B2e] and [Am, B1s]. A second B1 variant (the sequence of which is a chain based on partial cDNA sequences) from avian eye has been reported and overlapping cDNAs for a human variant B2 chain called laminin B2t have also been described.
Kalinin is an epithelium-specific laminin variant that is the major, if not the only component of the anchoring filament. (The anchoring filament is a characteristic ultrastructural component of the dermal-epidermal junction of skin believed to mediate the adhesion of the epithelium to the basement membrane.) The kalinin molecule contains three disulfide bond-linked polypeptide chains consisting of a 200-kD kalinin A chain (Ak), a 155-kD kalinin B2 chain (B2t), and a 140-kD kalinin B1 chain (B1k). Rotary shadowing of the molecule results in a 107-nm rod with globular domains at each end.
Kalinin is an epithelial-specific cell attachment factor utilized by skin keratinocytes for strengthening their attachment to the underlying dermis. Antibodies to the Ak chain cause the detachment of subconfluent karatinocytes from their growth substrate and deepithelization of intact skin.